Adding another girl for play time

I agree with roten27. Your bringing another girl to bed, for your relationship to be open enough and strong enough to handle that fact alone your girl should be fine with the question, however, that doesn't mean she'll say yes.

I would say that you should ask what is the worst that she could say No Right?

Well if you truly love her, it wouldn't matter if she smoked or not. Your Question was confusing so I don't know if this is the best answer.